<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>列表过渡</title>
  <script src="./vue.js"></script>
  <style>
    .v-enter, .v-leave-to {
      opacity: 0;
    }
    .v-enter-active, .v-leave-to {
      transition: opacity 1s;
    }
  </style>
</head>
<body>
  <div id="root">
    <transition-group>
      <div v-for="item of List" :key="item.id">{{item.title}}</div>
    </transition-group>
    <button @click="handleClick">add</button>
  </div>

  <script>
    var count = 0;
    var vm = new Vue({
      el: '#root',
      data: {
        List: []
      },
      methods: {
        handleClick: function() {
          this.List.push({
            id: count ++,
            title: "hello world"
          })
        }
      }
    })
  </script>
</body>
</html>